Reliability Analysis of Fatigue Crack Growth with JC Method Based on Scientific Materials

2011 ◽  
Vol 63-64 ◽  
pp. 882-885 ◽  
Author(s):  
Xiao Li Zou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Reliability Index ◽  
Limit State ◽  
State Equation ◽  
Fatigue Reliability ◽  
Crack Propagation Process ◽  
Log Normal

Since the fatigue crack propagation process from initial size till final fracture is affected by lots of random factors, it is difficult to evaluate the fatigue reliability. Based on reliability theory, the first order second moment method ( JC method) is adopted to analyze and compute the fatigue reliability. To account for the uncertainties of material resistance, the parameters in the deterministic fatigue crack growth rate equation and material fracture toughness are taken as random variables with Normal distribution or Log-Normal distribution. Consequently, the limit state equation of fatigue crack growth is derived. The fatigue reliability index at any moment is calculated iteratively through JC method. As a computation example, the curve of fatigue crack growth reliability index with time is presented.

Probabilistic Fatigue Safety Analysis of Oil and Gas Risers Under Random Loads

2010 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Oil And Gas ◽  
Growth Parameters ◽  
Limit State ◽  
Nonlinear Dynamic Analysis ◽  
Fatigue Reliability ◽  
Gas Drilling ◽  
Finite Element Software

Marine riser is an important component of oil and gas drilling and production system. It is essentially a slender pipe conveying fluid between well-head and floating production unit. They are formed out of three basic types of configuration namely, free hanging, “lazy-wave (SWLR)” riser. Risers are subjected to varied static, quasi-static and dynamic forces. For the safety of design, the behavior of the riser under these forces is thoroughly investigated. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element software package ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analyses of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially of fatigue crack growth parameters, is undertaken using bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Fatigue Reliability Assessment of Marine Risers in Deep Offshore Fields in Indian Ocean

2010 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Deep Sea ◽  
Failure Modes ◽  
New Ventures ◽  
Limit State ◽  
Published Data ◽  
Unstable Fracture ◽  
Fatigue Reliability

Depleting oil reserves in shallow water are opening the avenues of new ventures in deep sea conditions. India is no exception; deep sea explorations are highly recommended and exercised. As part of the design process, there are requirements of structural strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analysis of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear S-N curve and crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

scholarly journals Multiple Failure Modes Reliability Modeling and Analysis in Crack Growth Life Based on JC Method

2017 ◽  
Vol 2017 ◽  
pp. 1-5 ◽  
Author(s):  
YuanTao Sun ◽  
Chao Liu ◽  
Qing Zhang ◽  
XianRong Qin
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Failure Probability ◽  
Failure Modes ◽  
Limit State ◽  
State Equations ◽  
Multiple Failure Modes ◽  
Joint Failure

The fatigue crack growth (FCG) phenomenon generally exists in large mechanical structures. Due to the influences of varied kinds of random factors, the safety evaluation of structure in FCG is under great uncertainty. In this paper, based on the reliability theory, the limit state equations of fracture failure and static strength failure were derived firstly, and the parameters in those equations were regarded as random variables that follow the normal distribution or log-normal distribution. According to the limit state equations, the JC method (equivalent normalizing method) was used to calculate the reliability indexes under the different failure modes of structure in every stress cycle. Based on the reliability indexes and correlation of the two failure modes, the joint failure probability was obtained. In the end, a specific computation example was given, and the curve of joint failure probability in multiple failure modes was used for comparison with the result of single failure mode. The results indicated that the reliability analysis based on multiple failure modes was more reasonable, and the evaluation of reliability could be obtained in fatigue crack growth process.

Evaluations of some Stochastic Fatigue Crack Growth Models through Experimental Verification

2018 ◽  
Vol 928 ◽  
pp. 221-228
Author(s):  
Chih Chung Ni
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Growth Models ◽  
Random Factor ◽  
Normal Probability ◽  
Log Normal

The study is focused on the comparisons among three stochastic fatigue crack growth models through evaluations of experimental data. The first model assumed that the coefficient and exponent parameters of Paris-Erdogan law are mutually dependent normal random variables. The second model assumed that the fatigue crack growth rate equals to the deterministic Paris-Erdogan law multiplied by a stationary log-normal random factor while the third model proposed by the author was assumed that the fatigue crack growth rate equals to a deterministic polynomial in terms of fatigue crack size multiplied by a stationary log-normal random factor. Compact-tension specimens cut from a 2024-T351 aluminum-alloy plate were used for fatigue crack growth experiments under constant loads performed on thirty specimens. The normal probability paper for the first model was investigated to show the validity of the normal random parameter, and the log-normal probability papers for the second and third models were also investigated to show the validity of log-normal assumption of the random factors. The investigations on the probability of crack exceedance and distribution of random time of the three models were also made, and the comparisons of the results for all models were made as well.

Bi-Linear Fatigue and Fracture Approach for Safety Analysis of an Offshore Structure

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Parameters ◽  
Limit State ◽  
Steel Structures ◽  
Published Data ◽  
Offshore Structure ◽  
Structure Degradation

The design of welded structures for the fatigue limit state is normally carried out by means of either linear or bilinear S-N curves, which have been found adequate to predict crack initiation only. To properly assess the effects of the design, fabrication, inspection, and repair strategy for structure degradation due to crack growth, fracture mechanics (FM) models need to be applied. In this paper, alternative S-N and FM formulations of fatigue are investigated. The probabilistic fracture mechanics approach predicts the fatigue life of welded steel structures in the presence of cracks under random spectrum loading. It is based on a recently proposed bi-linear relationship to model fatigue crack growth. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bilinear crack growth relationship. Results pertaining to the fatigue reliability and fatigue crack size evolution are presented using the Monte Carlo simulation technique and the emphasis is placed on a comparison between the linear and bilinear crack growth models. Variations in the system configuration, service life, and coefficients of crack growth laws have been studied on the parametric basis

scholarly journals Investigation of fatigue crack growth under loading sequence effects using in-situ SEM testing

2018 ◽  
Vol 165 ◽  
pp. 22012
Author(s):  
Shan Jiang ◽  
Wei Zhang ◽  
Liang Cai ◽  
Zili Wang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Damage Zone ◽  
Shear Bands ◽  
Micro Cracks ◽  
Sequence Effects ◽  
Crack Propagation Process ◽  
Loading Sequence

Fatigue damage is one of the most important failure mechanisms in engineering components. The excited structures are usually subjected to spike loads in the fatigue weakness area during their service lives. The nonlinear loading sequence effects due to overloads are significant in the crack propagation process. In this paper, an in-situ scanning electron microscope (SEM) testing is performed to analyse the mechanisms of nonlinear fatigue crack growth affected by the load sequence. The crack tip behaviours under constant amplitude loading cycles superimposed by tensile overload were observed. The SEM experiment results reveal that the overload effects include the transient weakened area (shear bands and micro-cracks) and the relatively long-term retardation. Additionally, the observation loading sequence influence region is larger than the theoretical value. According to these SEM testing analyses, the Willenborg is modified considering the nonlinear loading sequence effects. In this approach, the damage zone concept is introduced to account for the instantaneous acceleration. Moreover, the loading sequence effect area is defined as the whole plastic zone due to overload rather than part of it. The proposed algorithm is validated by experiment data of 350WT steel and Al 2024-T351 specimens under constant loading with overloads. Good agreements are observed.

Evaluations of Stochastic Fatigue Crack Growth Models through Experimental Data

2016 ◽  
Vol 878 ◽  
pp. 132-136
Author(s):  
C.C. Ni
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Models ◽  
Compact Tension ◽  
Random Factor ◽  
Alloy Plate ◽  
Deterministic Function ◽  
Log Normal

The study is focused on the comparisons between a polynomial and power-law stochastic fatigue crack growth models through evaluations of experimental data. Both models were assumed that the fatigue crack growth rate equals to a deterministic function in terms of fatigue crack size multiplied by a stationary log-normal random factor. Compact-tension specimens cut from a 2024-T351 aluminum-alloy plate were used for fatigue crack growth experiments under random loads performed on twenty-five specimens. The log-normal probability papers for both models were investigated to show the validity of the log-normal assumption of the random factor . The investigations on the probability of crack exceedance and distribution of random time of the two models were also made, and the comparisons of the results for both models were made as well.

Nonlinear Dynamic and Bilinear Fatigue Performance of Composite Marine Risers in Deep Offshore Fields

2020 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Failure Modes ◽  
Thermal Protection ◽  
Growth Models ◽  
Limit State ◽  
Design Procedure ◽  
Crack Size ◽  
Unstable Fracture ◽  
Fatigue Reliability

Abstract Composite materials have drawn considerable consideration from the offshore business, basically because of their high explicit quality. Notwithstanding weight decrease, composites offer extra advantages, for example, fatigue resistance, damping, and thermal (protection) properties, and high erosion resistance. As a part of design procedure there are requirements of mechanical strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. Three dimensional nonlinear assessment of riser is carried out in time domain using ABAQUS/Aqua. The response time histories so obtained are used for the study of fatigue safety assessment of riser. It is based on a bi-linear approach to model fatigue crack growth and incorporates a failure limit to describe the interaction between rupture and plastic failure. Using Monte Carlo Simulation, tests of fatigue reliability and fatigue crack size evolution are obtained. It is observed that bilinear S-N curve and crack growth models leads to higher estimate of fatigue life. Sensitivity behavior pertinent to limit state adopted has been thoroughly examined. These outcomes implicate assessment of components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Time-variant fatigue reliability evaluation of riveted lap joint under stationary random loading

2020 ◽  
Vol 234 (4) ◽  
pp. 567-578
Author(s):  
Shan Jiang ◽  
Yan-Fu Li
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Growth Model ◽  
Reliability Assessment ◽  
Fatigue Reliability ◽  
Lap Joint ◽  
Random Loading ◽  
Crack Growth Model

This article focuses on the time-variant reliability assessment of riveted lap joint structure subjected to fatigue. A physics-based fatigue crack growth model that can take the crack closure into account is derived to calculate the crack length at different time under arbitrary loading. In addition, several uncertainties are quantified, including the material, initial crack size, and loading condition. The stationary random loading is a common service environment in practice, in which the stress range and stress ratio vary with constant statistical characteristics (the mean and standard deviation). The time-variant fatigue reliability of riveted lap joint under stationary random loading is assessed by introducing the outcrossing concept. The experimental data of 2024-T3 aluminum alloy riveted lap joint under constant amplitude loading are used to validate the physics-based fatigue crack growth model. It is verified that this proposed model can predict the fatigue life probability distribution with a reasonable accuracy. In addition, the simulation of riveted lap joint under stationary random loading is performed. The time-variant fatigue reliability is evaluated. The results with or without considering crack closures are also compared. It is noted that the results from the time-variant fatigue reliability assessment considering crack closure has higher reliability level.

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